1. Field of Invention
This invention relates to generally to overhead conveyor systems and more particularly to systems making use of an enclosed track in which a trolley is arranged to roll to support something from the trolley
2. Description of Related Art
Enclosed track conveyor systems are commonly used to support and carry items from a wheeled trolley located within the interior of an enclosed track. As is known enclosed tracks are hollow members having a top-wall, a pair of side walls projecting downward from the top wall and a pair of marginal flanges extending horizontally from respective ones of the side walls. The flanges are spaced from each other to form a slot therebetween. The trolley is located within the interior of the track, with its wheels or rollers disposed on the interior (upper) surface of the flanges.
Examples of enclosed track systems including internally located trolleys for rolling down the interior of the track are found in U.S. Pat. Nos.: 3,589,503 (Leach), 3,627,595 (Leach) and 6,450,326 (Hoffmann et al.). The trolleys of the foregoing patents are arranged so that they can negotiate curves in the track.
In some prior art system, the movement or rolling of a trolley down the interior of an enclose track is accomplished by use a tractor drive that is mounted on the trolley, but located outside of the track. Such tractor drives make use of a drive wheel which extends through the slot in the track to frictionally engage the inner surface of the top wall of the track. The drive wheel is rotated by a motor mounted on the externally located tractor. This arrangement requires that the drive wheel be of a relative large diameter. As a result such tractors are not suitable for use in systems wherein the enclosed track includes a relatively small radius curve, since the drive wheel would engage or bind in the slot. While some enclosed track systems make use of tractors having drive wheels that engage and ride on the bottom of the track, i.e., the inner surface of one or more of the flanges, such systems are not practical due to splices used on the track, which results in an uneven drive surface, and make it difficult to keep a constant pressure on the drive wheel.
Thus, the design of existing hoist trolley drives makes it impractical to drive a trolley through a curve in an enclosed track system and a need exists for an enclosed track system which achieves that end.
Other United States patents relating to the field of the subject invention are U.S. Pat. Nos. 3,774,548 (Borst), 3,518,947 (Borst), 3,855,941 (Fromme et al.), 6,178,891 (Ostholt et al.), 5,092,249 (Knuettel) and 2,710,319 (Bush) from Notice of References Cited in the Notice of Allowance of parent application Ser. No. 10/376,739.
All references cited herein are incorporated herein by reference in their entireties.